Image forming apparatus and method

ABSTRACT

It reduces a moving distance of a recording medium and thereby reduces the moving distance to be secured in an image forming apparatus so as to reduce size of the apparatus by a simple method. It is possible to feed a recording medium  304  at lower speed than normal speed on calibrating of a sensor unit  123  so as to reduce a distance passed by the recording medium  304.  It is possible to render the moving distance of the recording medium half by rendering feeding speed on the calibrating half the normal speed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image forming apparatus and amethod, and in particular, to a recording material determinationapparatus and method for detecting reflected light from a surface of arecording material and determining a kind thereof, and an image formingapparatus and method using the recording material determinationapparatus.

2. Description of the Related Art

An image forming apparatus such as a copying machine or a laser printertransfers an image visualized and developed by a development portion ona recording material and heats and pressurizes it under predeterminedfixing conditions so as to fix a developed image. The predeterminedfixing condition is significantly different depending on quality,thickness and surface treatment of the recording material. Therefore, adetailed setup according to a kind of recording material are requiredwhen using a plurality of kinds of recording material.

Conventionally, such an image forming apparatus has a size and a kind(kind of paper in the case where the recording material is paper) ofrecording material set up by a user on an operation panel provided onthe image forming apparatus proper for instance so as to change thefixing conditions (fixing temperature and feeding speed of the recordingmaterial passing through a fixing apparatus for instance) according tothat setup. Or else, there is a proposed method of having control meansfor setting it at a temperature lower than normal temperature andthereby solving adverse problems such as OHT twining on a fixing rolleroccurring in case of having an inkjet OHT (Over Head Transparency) otherthan prescribed paper mistakenly put through by the user and imagedegradation on a recording medium (refer to Japanese Patent ApplicationLaid-Open No. 2003-228256 for instance).

There is also a known method, not limited to the OHT, of calculatingdepth of asperities and asperity intervals on a recording medium surfacefrom a result of reading a surface image of the recording medium anddetermining the kind of recording medium such as gloss paper, plainpaper, rough paper or OHT so as to optimally set image formingconditions including printing density, transfer bias setup, fixingtemperature and process speed (refer to Japanese Patent ApplicationsLaid-Open Nos. 2003-302208 and 2001-225988 for instance).

Such image reading apparatuses mostly have degradation of shot imagesdue to variations in light volume caused by a light source or a lens.There are also variations in sensitivity in photoelectric cells of animage pickup device. For this reason, there is a thinkable method, forthe sake of accurately reading an object and obtaining a correct imagingresult, of shooting for measuring a shading amount a plurality of timesin a state of having the recording medium moved and averaging shootingresults thereof so as to automatically calculate the shading amount andcorrect the shooting results.

In the case of the above-mentioned image forming apparatus, however, itis necessary to shoot a plurality of times in the state of having therecording medium moved. For that reason, there is a problem that asufficient area for having the recording medium moved must be secured inthe image forming apparatus and so the apparatus becomes large.

SUMMARY OF THE INVENTION

The present invention has been made in view of such problems, and has anobject to improve a conventional apparatus to provide an apparatus andmethod that can maintain an accuracy in determining of recordingmaterial without increasing the size of the apparatus. It determines arecording medium in a configuration using an image pickup device and alens without being influenced by unevenness in detection distributioncaused by a light source, a lens or the image pickup device. In thisregard, an object of the present invention is to provide image formingapparatus and method which are simple and keep required accuracy withoutincreasing size of the apparatus.

To attain this object, an image forming apparatus of the presentinvention comprises: feeding means for feeding a recording material atpredetermined speed in a predetermined direction; image forming meansfor forming an image on the recording material fed by the feeding means;light irradiation means for irradiating light on the recording material;and image reading means for reading the light irradiated by the lightirradiation means and reflected from a surface of the recording materialand thereby obtaining the image on the surface of the recordingmaterial; and reflective type determination means, including the lightirradiation means and the image reading means, for having the image onthe surface of the recording material read by the image reading meanswhile having the recording material fed by the feeding means so as todetermine a predetermined attribute of the recording material by usingobtained image on the surface of the recording material, wherein theapparatus determines a kind of recording material based on the attributeobtained by the reflective type determination means to form the image onthe recording material, and the reflective type determination meansincludes feeding control means for, on having the recording materialread by the image reading means, controlling the feeding means to rendera moving distance shorter then than that in the case of feeding it atthe predetermined speed.

Another image forming apparatus of the present invention comprises:feeding means for feeding a recording material at predetermined speed ina predetermined direction; a latent image supporting element forsupporting a latent image; developing means for visualizing the latentimage as a developed image by providing a developer to the latent imagesupporting element; transfer means for transferring the developed imageof the developing means to the recording material fed by the feedingmeans; fixing means for fixing the recording material having thedeveloped image transferred thereon by the transfer means; lightirradiation means for irradiating light on the recording material; andimage reading means for reading the light irradiated by the lightirradiation means and reflected from a surface of the recording materialand thereby obtaining the image on the surface of the recordingmaterial; and reflective type determination means, including the lightirradiation means and the image reading means, for having the image onthe surface of the recording material read by the image reading meanswhile having the recording material fed by the feeding means so as todetermine a predetermined attribute of the recording material by usingobtained image on the surface of the recording material, wherein theapparatus determines a kind of recording material based on the attributeobtained by the reflective type determination means to form thedeveloped image on the recording material under an image forming processcondition corresponding to the determined kind, and the reflective typedetermination means includes feeding control means for, on having therecording material read by the image reading means, controlling thefeeding means to render a moving distance shorter then than that in thecase of feeding it at the predetermined speed.

Furthermore, an image forming method of the present invention comprises:a feeding step of feeding a recording material by feeding means atpredetermined speed in a predetermined direction; a step of developingand fixing an image by developing and fixing means on the recordingmaterial fed by the feeding means; an image reading step of, whilefeeding the recording material by feeding means, reading by imagereading means the light irradiated by light irradiation means forirradiating light on the recording material and reflected from a surfaceof the recording material and thereby obtaining the image on the surfaceof the recording material; a reflective type determination step,including the image reading step, of performing the image reading stepso as to determine a predetermined attribute of the recording materialby reflective type determination means by using obtained image on thesurface of the recording material; and a step of determining a kind ofthe recording material based on an obtained attribute, wherein thereflective type determination step includes a step of, on having therecording material read by the image reading means, having the feedingmeans controlled by feeding control means to render a moving distanceshorter then than that in the case of feeding it at the predeterminedspeed.

A recording material determination apparatus of the present inventioncomprises: an image reading portion for irradiating light on a recordingmedium and reading light reflected from a surface of the recordingmedium and thereby obtaining an image on the surface of the recordingmedium; a feeding portion for feeding the recording medium at apredetermined speed; a feeding control portion for, on having the imageon the recording medium read by the image reading portion, controllingthe feeding portion to feed the recording medium in a different feedingstate from the feeding state in the case of feeding it at thepredetermined speed; and a determination portion for having the image onthe surface of the recording medium read by the image reading portionwhile having the recording medium fed in the different feeding state bythe feeding portion so as to determine an attribute of the recordingmedium by using obtained images on the surface of the recording medium.

A recording material determination method of the present inventioncomprises: a feeding step of feeding a recording medium at apredetermined speed; an image reading step of irradiating light on therecording medium and reading the light irradiated and reflected from asurface of the recording medium and thereby obtaining an image on thesurface of the recording medium; a feeding control step of, in the imagereading step, controlling the feeding operation of the recording mediumto feed the recording medium in a different feeding state from thefeeding state in the case of feeding it at the predetermined speed; anda determination step of having the image on the surface of the recordingmedium read, while feeding the recording medium in a different feedingstate from the feeding state in the case of feeding it at thepredetermined speed in the image reading step so as to determine anattribute of the recording medium by using obtained image on the surfaceof the recording medium.

An image forming apparatus comprising: a feeding portion for feeding therecording medium at a predetermined speed; an image forming portion forforming an image on the recording material fed by the feeding portion;an reading portion for irradiating light on a recording medium andreading light reflected from a surface of the recording medium andthereby obtaining an image on the surface of the recording medium; acontrol portion for having the image on the surface of the recordingmedium read by the reading portion while having the recording medium fedin a different feeding state by the feeding portion so as to change animage forming condition of the image forming portion by using obtainedimages on the surface of the recording medium.

The above and other objects, effects, features and advantages of thepresent invention will become more apparent from the followingdescription of embodiments thereof taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing an image forming apparatus used in afirst embodiment of the present invention;

FIG. 2 is a diagram showing a configuration of each unit controlled by acontrol CPU according to an embodiment of the present invention;

FIG. 3 is a pattern diagram showing an overview configuration fordetecting a reflected light volume of a recording material;

FIG. 4 is a diagram showing a contrast between an analog image on asurface of the recording material read by a CMOS sensor of an imagereading sensor according to an embodiment of the present invention and adigital image having digitally processed an output from the CMOS sensorto 8×8 pixels;

FIG. 5 is a flowchart showing operation of the control CPU according toan embodiment of the present invention;

FIG. 6 is a diagram showing a circuit block diagram of the CMOS sensor;

FIG. 7 is a block diagram showing a control circuit of the CMOS sensor;

FIG. 8 is a diagram schematically showing a measurement area forperforming shading measurement obtained by being irradiated by anirradiation apparatus of a conventional sensor portion;

FIG. 9 is a diagram schematically showing the measurement area forperforming the shading measurement obtained by being irradiated by theirradiation apparatus of the sensor portion according to an embodimentof the present invention;

FIGS. 10 are diagrams showing images obtained by irradiating light onthe recording material;

FIG. 11 is a diagram showing a difference between normal feeding andfeeding of the sensor portion according to an embodiment of the presentinvention;

FIG. 12 is a diagram showing a difference between the normal feeding andthe feeding of the sensor portion according to an embodiment of thepresent invention; and

FIG. 13 is a diagram showing a difference between and timing of thenormal feeding and the feeding of the sensor portion according to anembodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

Hereunder, an image forming apparatus and a method according to thepresent invention will be described by referring to the drawings.

The present invention is used in a general image forming apparatus asshown in FIG. 1. In FIG. 1, an image forming apparatus 101 comprises apaper cassette 102, a paper feed roller 103, a feeding roller 124, a topsensor 125, a transfer belt driving roller 104, a transfer belt 105,yellow, magenta, cyan and black photoconductive drums 106 to 109,transfer rollers for the colors 110 to 113, yellow, magenta, cyan andblack cartridges 114 to 117, yellow, magenta, cyan and black opticalunits 118 to 121 and a fixing unit 122.

The image forming apparatus 101 comprises as image forming means, anoptical unit, a photosensitive drum, the transfer belt 105, and thefixing unit 122, and generally uses an electrophotographic process totransfer yellow, magenta, cyan and black images one upon another on arecording material, and controls temperature of a toner imagetransferred by the fixing unit 122 including fixing rollers so as tothermally fix it. The optical units 118 to 121 in the colors areconfigured to form a latent image by performing an exposure scan onsurfaces of the photoconductive drums 106 to 109 with a laser beam.These series of image forming operations are synchronized to have theimages transferred from a predetermined position on the recordingmaterial to be fed.

Furthermore, the image forming apparatus 101 comprises a paper feedmotor for supplying and feeding recording paper as the recordingmaterial, and the fed recording paper has a desired image formed on itssurface while being fed to the transfer belt and fixing roller.

Supplied recording paper is fed by a feeding roller 124 at a presetspeed. The front edge of the recording paper is detected by the topsensor 125, and when a predetermined time has passed after thedetection, the feeding operation for the recording paper is temporallystopped. In this temporal stopped state, the surface image of therecording paper is read by the sensor unit 123. Imaging is performed forthe shading measurement mentioned above multiple times before thetemporal stop.

A sensor unit 123 is placed before the recording paper is fed to thetransfer belt, and irradiates light on the surface of the fed recordingmaterial to focus reflected light thereof and form an image so as toread the image in a specific area on the surface of the recordingmaterial.

A control CPU 210 as control means of the image forming apparatus 101will be described below by referring to FIG. 2. The control CPU 210provides a desired amount of heat to the recording material by means ofthe fixing unit 122 so as to fusion-bond and fix the toner image on therecording material.

Next, a description will be given by using FIG. 2 as to the operation ofthe control CPU of the image forming apparatus and method according toan embodiment of the present invention. FIG. 2 is a diagram showing aconfiguration of each unit controlled by the control CPU 210. In FIG. 2,the control CPU 210 is connected to a CMOS sensor 211 and the opticalunits for the colors 212 to 215 including polygon mirrors, motors andlasers, and controls the optical units for the colors in order to scan alaser on the surfaces of the photoconductive drums and draw a desiredlatent image. Likewise, the control CPU 210 controls a paper feed motor216 for feeding the recording material, a paper feed solenoid 217 usedto start driving the paper feed roller for feeding the recordingmaterial, a paper existence sensor 218 for detecting whether or not therecording material is set at a predetermined position, a high-voltagepower supply 219 for controlling primary charging, development, primarytransfer and secondary transfer biases necessary for theelectrophotographic process, a drum driving motor 220 for driving thephotoconductive drums and transfer rollers, a belt driving motor 221 fordriving the rollers of the transfer belt and fixing unit, the fixingunit and a low-voltage power supply unit 222. Furthermore, the controlCPU 210 monitors the temperature with a thermistor (not shown) so as toexert control to keep fixing temperature constant.

The control CPU 210 is also connected to a memory 224 by a bus and so on(not shown), and the memory 224 stores programs and data for executingall or a part of the processes performed by the control CPU 210 in theabove control and the embodiments described herein. To be more specific,the control CPU 210 performs the operations of the embodiments of thepresent invention by using the programs and data stored in the memory224.

The ASIC 223 is a hardware circuit that controls motor speed inside theCMOS sensor 211 and optical units 212 to 215 and also controls speed ofthe paper feed motor based on an instruction of the control CPU 210. Asfor speed control of the motors, it detects a tack signal from the motor(not shown) and exerts the speed control by outputting an accelerationsignal or a deceleration signal to the motor so that an interval of thetack signal becomes a predetermined time. Since speed control isperformed for multiple motors, it is more advantageous to construct thecontrol circuit from a hardware circuit of ASIC 223 than using softwarecontrol, so as to reduce a control load of the control CPU 210.

On receiving a print command of an instruction from a host computer (notshown), the control CPU 210 determines whether or not the recordingmaterial exists by means of the paper existence sensor 218. If the paperexists, the control CPU 210 drives the paper feed motor 216, drumdriving motor 220 and belt driving motor 221, and also drives the paperfeed solenoid 217 to feed the recording material to the predeterminedposition.

If the recording material is fed to the position of the CMOS sensor 211after a predetermined time passed from the detection of the front edgeof the recording paper by the top sensor 125, the control CPU 210provides a CMOS sensor 211 imaging instruction to the ASIC 223 so thatthe CMOS sensor 211 images a surface image of the recording material. Inthis case, the ASIC 223 activates Sl_select and then outputs SYSCLK of apredetermined pulse in predetermined timing so as to capture imagingdata outputted from the CMOS sensor 211 via Sl_out.

As for gain setting of the CMOS sensor 211, it sets a value determinedin advance by the control CPU 210 on a register inside the ASIC 223 sothat the ASIC 223 activates Sl_select and then outputs SYSCLK of thepredetermined pulse in predetermined timing to set a gain of the CMOSsensor 211 via Sl_in.

The ASIC 223 comprises a control circuit 702 for implementing arecording material determination apparatus and a method thereof of thepresent invention described below, and a result of calculation fordetermining an attribute of the recording material is stored in aregister A and a register B inside the control circuit 702. And thecontrol CPU 210 reads the calculation result for determining theattribute of the recording material stored in the register A andregister B inside the control circuit 702, and determines the kind ofthe supplied recording material so as to exert control to change imageforming conditions according to the result.

The following can be named as various kinds of control of the imageforming conditions executed by the control CPU 210. For instance, in thecase of so-called rough paper wherein surface texture of the recordingmaterial is rough, the control is exerted to render a development biaslower than that of plain paper and curb a toner amount adhering to thesurface of the recording material so as to prevent the toner fromspattering. This is intended to solve the problem that, especially inthe case of the rough paper, the toner spatters due to paper texture anddegrades image quality because of a large toner amount adhering to thesurface of the recording material.

The control CPU 210 also determines the kind of the supplied recordingmaterial, and variably controls a temperature condition of a fixing unit22 according to the result. This is effective, in the case of the OHT inparticular, as to the problem that transparency of the OHT degrades iffixability of the toner adhering to the surface of the recordingmaterial is bad.

Furthermore, the control CPU 210 also determines the kind of thesupplied recording material, and variably controls feeding speed of therecording material according to the result. The feeding speed iscontrolled by having a speed control register value of the ASIC 223 forexerting the speed control set by the control CPU 210. For instance, inthe case of a transparent recording material such as the OHT, a fixingtemperature condition is changed, and the control is exerted to increasethe fixing temperature in order to increase the transparency. It is alsopossible to exert the control to change the feeding speed of therecording material depending on whether or not the kind of the recordingmaterial is a transparent type. Furthermore, in the case of the glosspaper, it is possible to increase the fixability of the toner adheringto the surface of the recording material so as to improve the gloss andenhance the image quality.

Thus, according to this embodiment, the calculation is performed by ahardware circuit by the ASIC from the surface image of the recordingmaterial imaged by the CMOS sensor. From the result of the calculation,the CPU can exert the control to change a development bias condition ofthe high-voltage power supply, the fixing temperature of the fixing unitor the feeding speed of the recording material.

First Embodiment

Next, a description will be given as to the recording materialdetermination apparatus according to an embodiment of the presentinvention. FIG. 3 is a pattern diagram showing an overview configurationfor detecting a reflected light volume of the recording material.

As shown in FIG. 3, the sensor unit 123 comprises a reflection LED 301which is light irradiation means, a recording material 304, the CMOSsensor 211 which is reading means and an imaging lens 303. Here, theCMOS sensor 211 may be a CCD sensor.

The light of which light source is the reflection LED 301 is irradiatedtoward the surface of the recording material 304. The light source isthe LED according to this embodiment. However, it is also possible touse a xenon tube or a halogen lamp. The reflected light from therecording material 304 is focused via the imaging lens 303 to be imagedon the CMOS sensor 211. It is thereby possible to read the image on thesurface of the recording material 304.

According to this embodiment, the reflection LED 301 is placed toobliquely irradiate LED light on the surface of the recording material304 at a predetermined angle as shown in FIG. 3. However, it is alsopossible, instead of obliquely mounting the LED, to obliquely irradiatethe light with a light guide not shown.

FIG. 4 is a diagram showing a contrast between an analog image on thesurface of the recording material 304 read by the CMOS sensor 211 of thesensor unit 123 and a digital image having digitally processed an outputfrom the CMOS sensor 211 to 8×8 pixels. Here, digital processing isperformed by converting an analog output from the CMOS sensor 211 to8-bit pixel data by A/D conversion.

In FIG. 4, a recording material A401 is so-called rough paper of whichpaper texture on the surface is relatively rough, a recording materialB402 is so-called plain paper generally used, and a recording materialC403 is so-called gloss paper, where enlarged surface images thereof areshown respectively. These images 401 to 403 read by the CMOS sensor 211are digitally processed to become images 404 to 406 shown in FIG. 4respectively. Thus, the images on the surface are different depending onthe kind of recording material. This is a phenomenon occurring mainlydue to different states of the texture on the surface of the paper.

Apart from this, a reflected light volume of the recording material isgenerally calculated from a total or an average of the light inputted tothe respective pixels. It is also possible, however, to use the resultof only one light-receiving pixel depending on the embodiment.

As described above, it is possible to identify a surface state of thepaper texture of the recording material from the image which is adigitally processed image of the result of reading the surface of therecording material with the CMOS sensor 211. In addition, it is possibleto determine the recording material by the reflected light volume.

To identify the surface of the recording material, a part of the surfaceof the recording material is read as the digital image comprised of 8×8pixels, and a pixel density Dmax as a maximum density and a pixeldensity Dmin as a minimum density per line in a direction orthogonal toa feeding direction of the recording material in the image are detectedso as to obtain Dmax−Dmin, which is given from each line, for eightlines. And a quality of material (smoothness) as the attribute of therecording material can be determined by the value of Dmax−Dmin obtainedby averaging.

To be more specific, in the case where the paper texture on the surfaceis rough as in the case of the recording material A, a large number ofshadows of the texture are generated. Consequently, differences betweenbright locations and dark locations become significant so that Dmax−Dminbecomes larger. In the case of the image on the surface of the recordingmaterial, such as the recording material C, of which texture issufficiently compressed and smoothness is high, there are a smallernumber of shadows of the texture so that Dmax−Dmin becomes smaller. Thequality of the recording material is determined by this comparison,which is a part of information for determining the kind.

The image data may be binarized to obtain edge number data for each linethereby determining the surface unevenness. The edge number data may be,for example, obtained by assigning “1” to white portion and “0” to blackportion and counting the number of “1” data portion in each line.

The surface state of the recording paper can be recognized using thevalue of Dmax−Dmin and the edge number data.

Thus, the images obtained by irradiating the light on the surface of therecording material are different depending on the kind of the recordingpaper. This is a phenomenon arising mainly because the state of thetexture on the surface of the paper and the state of compression of thetexture of the paper are different.

The above-mentioned control processor is required to perform a samplingprocess of the images from the CMOS sensor 211 and gain and filtercalculation processes in real time. Therefore, it is desirable to use adigital signal processor.

Next, the control circuit of the CMOS sensor 211 will be described byusing FIG. 7. FIG. 7 is a block diagram showing the control circuit ofthe CMOS sensor 211. In FIG. 7, the control CPU 210 as a determinationportion comprises the control circuit 702, the CMOS sensor 211, aninterface control circuit 704, a calculation circuit 705, a registerA706, a register B707 and a control register 708.

Next, the operation will be described. The control CPU 210 provides dataindicating an operation instruction of the CMOS sensor 211 to thecontrol register 708, and then the CMOS sensor 211 starts imaging theimage on the surface of the recording material. To be more specific,accumulation of electric charges on the CMOS sensor 211 is started. TheCMOS sensor 211 is selected by Sl_select from the interface controlcircuit 704 and SYSCLK is generated in predetermined timing so thatimaged digital image data is sent from the CMOS sensor 211 via theSl_out signal.

The imaging data received via the interface control circuit 704 iscalculated by the control circuit 702, and the result of the calculationis stored in the registers A706 and B707. The control CPU 210 determinesthe attribute of the recording material from the values of the tworegisters.

The imaging data received via the interface control circuit 704 issubject to a predetermined calculation by the calculation circuit of thecontrol circuit 702, and, as the result, a value is stored into theregister A 706, which value is the average of values of Dmax−Dmin foreight lines, which is the difference data between the density Dmax ofthe pixel with a maximum density and the density Dmin of the pixel witha minimum density on the surface of the recording paper.

The imaging data received via the interface control circuit 704 issubject to a predetermined calculation by the calculation circuit of thecontrol circuit 702, and the calculation result is stored into theregister B 707 as edge number data of the recording paper surface (totalvalue of the edge number for lines, for example). CPU 701 determines theevenness of the recording material, that is an attributes of therecording material, from the above two values of the registers.

Next, a sensor circuit block diagram will be described by using FIG. 6.FIG. 6 is a diagram showing a circuit block diagram of the CMOS sensor.In FIG. 6, a CMOS sensor portion 601 has a sensor equivalent to 8×8pixels placed like an area therein. Furthermore, vertical shiftregisters 602 and 603, an output buffer 604, a horizontal shift register605, a system clock 606 and a timing generator 607 are placed inaddition.

Next, the operation will be described. On activating a Sl_select signal613, the CMOS sensor portion 601 starts the accumulation of electriccharges based on received light. Next, when the system clock 606 isgiven, the vertical shift registers 602 and 603 sequentially select rowsto be read by means of the timing generator 607 so as to sequentiallyset the data to the output buffer 604.

The data set to the output buffer 604 is transferred to an A/D converter608 by the horizontal shift register 605. The pixel data digitized bythe A/D converter 608 is controlled in predetermined timing by an outputinterface circuit 609, and is outputted to an Sl_out signal 610 during aperiod when the Sl_select signal 613 is active.

A description will be given as to the operation of an embodiment forimplementing the present invention by using the above sensors, controlcircuits and so on. Reference numerals 801 to 808 of FIG. 8schematically show measurement areas for performing shading datameasurement obtained by being irradiated by an irradiation apparatus ofa conventional sensor portion. Likewise, reference numerals 901 to 908of FIG. 9 schematically show the measurement areas for performing theshading data measurement obtained by being irradiated by the irradiationapparatus of the sensor portion according to an embodiment of thepresent invention.

First, a description will be given as to a principle of elimination ofimage reading noise used in this embodiment. To simplify thedescription, by way of example, the case of shooting an image such as(9) of FIG. 10 will be considered assuming the case of shooting with theCMOS sensor of 64 pixels of 8×8 pixels a page. The image of (9) includesa character “A” of a target shooting image and shading components of anoptical system and an illumination system together. First, eight imagesfor calibrating are shot while a shooting object is fed and moving. Theshot images are (1) to (8) of FIG. 10. It is necessary to average theimages for calibrating because they include noise components due to duststicking to a detected object and irradiation unevenness of theirradiation apparatus which are nontarget information. To be morespecific, it is possible, by means of averaging, to calculate unchangedcomponents (such as the shading components and variations in pixelsensitivity) which are the image reading noise data even though theshooting object changes.

(10) of FIG. 10 shows the image data after the averaging. A desiredimage is shot after performing the shooting and averaging as above. Inthis case, images for correction may be shot after performing the targetshooting. As the result of shooting the desired image is the image (9)of FIG. 10, it is possible to make a correction thereto with an averagedimage (10) having only the shading components calculated so as toeliminate the shading components. Thus, the character “A” which is adesired shooting image can be obtained more clearly. (11) of FIG. 10shows the image obtained by thus making a correction.

According to this embodiment, this principle is used to obtain a moreaccurate image on the surface of the recording material so as todetermine a characteristic of the recording material, such as the roughpaper with a rough surface or the gloss paper with a fine surface. To bemore precise, shading data, which is the image reading noise datagenerated due to the unevenness of irradiation of the irradiationapparatus and so on, is calculated first from a plurality of imagesobtained by shooting the surface with the sensor a plurality of times(eight times in the above-mentioned example) while feeding the recordingmaterial. Next, the surface is shot once in a state of stopping theshooting of the recording material, and shading data, which is the imagereading noise obtained as above, is eliminated from the shot image.Thus, it is possible to obtain a more adequate surface image of therecording material.

The time period required for one imaging by the CMOS sensor ispredetermined (or depends on the specification of the CMOS sensor),which is the time period for obtaining image data required for thedetermination of recording material. The imaging interval of the sensorunit 123 (time interval between multiple times of imaging) is set basedon the time period required for one imaging.

Here, description will be made for the relation between the calculationof the above-described reading operation of the surface image andshading data and the feeding operation of recording material (see FIG.1).

Paper supplied from the paper cassette 102 is fed to the feeding roller124, and the surface image of the recording paper is read multiple timesafter a predetermined time period passed from the timing of thedetection of the front edge of the paper by the top sensor 125. Thepredetermined time period is a time period required for reaching theposition at which the paper can be imaged by the sensor unit 123, and isdetermined in advance based on the speed of the paper supply and thedistance to the sensor unit 123.

The recording paper is being fed in the multiple reading operations.Shading data is calculated using the multiple read images. Then, therecording paper is temporally stopped, and the surface image of therecording paper is read again. A surface image of the recording paper isobtained from the image read by the reading operation and the shadingdata.

In the conventional image forming apparatus shown in FIG. 8, the feedingspeed with which the feeding of the recording material is restarted isset at a normal speed that is determined in advance. The normal speed isan image forming speed with which an image is formed on plain paper.

As described above, the above process has the recording material 304which is the recording medium fed to shoot the images for calibrating.In the case of feeding at normal speed, that is, the same feeding speedas when developing and fixing the images (i.e. forming an image) on therecording material 304 as with the conventional image forming apparatusshown in FIG. 8, the recording material 304 passes significantly belowthe sensor unit 123. For this reason, it is necessary for the imageforming apparatus to incorporate an area large enough to hold therecording material 304 having passed behind the sensor unit 123 (aconfiguration for extending the feeding speed). Under normal conditions,a next feeding portion such as the transfer belt driving roller 104 ismounted behind the sensor unit 123 as shown in FIG. 1, and is adapted toperform a preprinting operation at a very close position to where therecording material 304 is supplied. For that reason, a sufficientdistance is required between the sensor unit 123 and the transfer beltdriving roller 104 for the recording material 304 to feed, decelerateand stop from the sensor unit 123 onward. Therefore, the conventionalimage forming apparatus could not avoid its housing from becominglarge-size by any means since there is a substantial distance of themoving of the recording paper.

Thus, according to the present invention, it is possible to feed therecording material 304 at lower speed than normal speed on calibratingof the sensor unit 123 so as to reduce the distance by which therecording material 304 passes beyond the sensor unit 123. FIG. 9 showsthe moving distance of the recording material is reduced relative to thecase of FIG. 8 showing a feeding state of conventional art. FIG. 11shows a moving distance of the recording medium as against the timethen. FIG. 11 shows that the moving distance of the recording medium canbe half by rendering the feeding speed on calibrating (2) half thenormal speed (1). FIG. 5 is a flowchart showing the above operation.Each step will be described.

-   S501: Operation of determining recording material starts.-   S502: It is determined whether determination of the recording    material is to be performed.    Here, the process ends in the case where the user have decided in    advance that the determination is unnecessary (NO).-   S503: The recording material is fed at a speed lower than the speed    in image forming that is set in advance for the recording material    (normal speed).-   S504: Reading of image is performed multiple times with the    recording material being fed at a low speed.-   S505: It is determined whether the reading is completed. Here, the    process returns to S503 if the reading is not completed (NO).-   S506: Image reading noise data (shading data) for eliminating    radiation unevenness is calculated using multiple images read at    S504.-   S507: An image of the surface of the recording material is read with    the moving of the recording material not performed.-   S508: The recording material is determined using the image read at    S506 and the image reading noise data calculated at S507.-   S509: End of the determination operation.    Here, the control operation according to the flowchart in FIG. 5 is    performed by the CPU 210.

As described above, it is possible, by rendering the speed of therecording medium slower than the normal speed on calibrating of thesensor, to reduce the distance from the sensor to the next feedingportion so as to provide the image forming apparatus of which apparatusproper is small. Further, it is possible to keep the accuracy in imagingof shading data so as to maintain the accuracy in the determination ofthe recording material.

According to this embodiment, the control is exerted to shoot thesurface of the recording material once in the state of stopping thefeeding of the recording material after shooting a plurality of timeswhile moving the recording material. However, it is not limited theretobut it is also possible to shoot the surface of the recording materialonce in the state of stopping it first and then shoot a plurality oftimes while moving the recording material so as to eliminate the imagereading noise (shading component).

Second Embodiment

Next, a second embodiment will be described. As its basic configurationand control are the same as that of the first embodiment, only thedifferences will be described by omitting detailed description of theconfiguration in common. As for the first embodiment, the configurationfor reducing the feeding speed of the recording medium on calibrating ofan imaging sensor (on measuring the shading data) was described. On anactual image forming apparatus, however, motor revolutions and a gearratio are set to optimize a motor torque for the normal speed.Therefore, on switching to low speed, depending on the setting of themotor revolutions and gear ratio for the normal speed, the motor torquemay become insufficient and cause revolution trouble. For this reason,there are the cases where stable feeding can no longer be secured ifsimply switched to the low speed.

The repeated operation of feeding and stopping according to theembodiment is controlled so that recording material is fed by repeatingof feeding and stopping at S503 in the flowchart of FIG. 5.

Thus, according to this embodiment, the control is exerted to repeat thefeeding and stopping of the recording medium so as to reduce the movingdistance of the recording medium. The moving distance of the recordingmedium versus time in this case is shown in FIG. 12. In FIG. 12, thefeeding speed on moving (2) is equivalent speed to normal feeding speed(1), where a feeding distance of a moving medium is reduced by providinga stop time after moving for a predetermined time. According to thisembodiment, the speed while moving is the same as the normal speed.However, this may also be different speed from the normal speed. To bemore specific, without slowing down feeding operation causingunstableness, for example, the time period required for thedetermination of the recording material maybe reduced by increasing thefeeding speed higher than the normal speed, or the speed may be anyspeed as long as the object of the present invention can be achieved.

As described above, it is possible to shoot the recording material 304while moving and stopping it on calibrating of the sensor unit 123 andthereby render a moving distance of the recording medium shortercompared to the cases of feeding at the normal speed. Therefore, it ispossible to reduce the distance from the sensor unit 123 to the nextfeeding portion so as to provide the image forming apparatus of whichapparatus proper is small. Further, it is possible to keep the accuracyin imaging of shading data so as to maintain the accuracy in thedetermination of the recording material.

As for timing of shooting, it should be performed in predetermined andarbitrary timing (interval).

Third Embodiment

Next, a third embodiment will be described. As its basic configurationand control are the same as that of the first and second embodiments,only the differences will be described by omitting detailed descriptionof the configuration in common. As for the second embodiment, theconfiguration for reducing the moving distance by repeating the movingand stopping of the recording medium was described. In this embodiment,the timing for moving and stopping the recording material 304 issynchronized with the timing for imaging of the sensor unit 123, therebyallowing an efficient calibration. Specifically, the recording medium ismoved at the moment of the imaging to perform efficient calibrating.

FIG. 13 shows the time in that case and the moving distance of therecording material 304. The sensor unit 123 repeatedly performs theimaging in fixed timing. The sensor unit 123 shoots the image of therecording material 304 in the area in which sensor detection timing (3)shown on top of FIG. 13 is High. To perform the calibrating of thesensor unit 123 without being influenced by a surface property of therecording material 304, the position of the imaging on the recordingmedium should be different between the imaging of last time and that ofthis time. It is also possible, if the recording medium is moving at themoment of the imaging, to perform the calibrating with less influence ofthe surface property of the recording medium. This is because theinfluence of the surface feature of the recording material is morereduced for the imaging in a static state than the imaging in a movingstate, and therefore, shading data for compensating the variation inlight amount due to the light source or lens is easily measured in theformer case.

Thus, it is most efficient to move the recording medium by a requisiteminimum distance once in timing for imaging of the sensor unit 123 andkeep it suspended otherwise. As shown in FIG. 13, the recording mediumrepeatedly moves and stops like the feeding speed on calibrating (2) asagainst the timing of the sensor unit 123 shooting the image on therecording material 304 (3). In this case, the recording medium movesonce per imaging. It thus stops after moving and shooting necessarynumber of times. It is thereby possible to render the moving distance ofthe recording medium minimal. Here, it shows an example in which thedetection timing of the sensor unit 123 is not continuous but separate.However, the detection timing can be continuous. And it moves once perdetection timing in the example in this embodiment. However, theshooting (detection) may be twice or more if the moving distance isslower than that of the normal speed.

As described above, the moving and stopping of the recording medium aresynchronized with the detection timing of the sensor unit 123 oncalibrating thereof (that is, on measuring of shading data) so that asubstantial accuracy of the sensor calibration can be ensured therebyachieving an excellent accuracy of the determination of a recordingmedia. Also, the moving distance of the recording material 304 becomesminimal and therefore, it is possible to reduce the distance from thesensor unit 123 to the next feeding portion so as to provide the imageforming apparatus of which apparatus proper is small. It is alsopossible to secure sufficient accuracy of the calibrating of the sensorand accurately determine the recording medium. Therefore, it is possibleto provide the image forming apparatus capable of setting optimal imageforming conditions and forming high-accuracy images.

According to the present invention, the image forming apparatuscomprises: feeding means for feeding the recording material atpredetermined speed in a predetermined direction; image forming meansfor forming an image on the recording material fed by the feeding means;light irradiation means for irradiating light on the recording material;and image reading means for reading the light irradiated by the lightirradiation means and reflected from the surface of the recordingmaterial and thereby obtaining the image on the surface of the recordingmaterial; and reflective type determination means, including the lightirradiation means and the image reading means, for having the image onthe surface of the recording material read by the image reading means aplurality of times so as to determine a predetermined attribute of therecording material by using a plurality of obtained images on thesurface of the recording material, wherein the apparatus determines thekind of the recording material based on the attribute obtained by thereflective type determination means to form the image on the recordingmaterial, and the reflective type determination means includes feedingcontrol means for, on having the recording material read by the imagereading means, controlling the feeding means to render the movingdistance shorter then than that in the case of feeding it at thepredetermined speed. Therefore, it is possible to reduce the movingdistance of the recording medium and thereby reduce the moving distanceto be secured in the image forming apparatus so as to reduce the size ofthe apparatus by a simple method.

The present invention has been described in detail with respect topreferred embodiments, and it will now be apparent from the foregoing tothose skilled in the art that changes and modifications may be madewithout departing from the invention in its broader aspect, and it isthe intention, therefore, in the apparent claims to cover all suchchanges.

This application claims priority from Japanese Patent Applications Nos.2004-101221 filed Mar. 30, 2004 and 2005-073784 filed Mar. 15, 2005,which are hereby incorporated by reference herein.

1. An image forming apparatus comprising: feeding means for feeding arecording material at predetermined speed in a predetermined direction;image forming means for forming an image on the recording material fedby the feeding means; reflective type determination means includinglight irradiation means for irradiating light on the recording material,image reading means for reading the light irradiated by the lightirradiation means and reflected from a surface of the recording materialand thereby obtaining the image on the surface of the recordingmaterial, and feeding control means for, on having the recordingmaterial read by the image reading means, controlling the feeding meansto render a moving distance shorter than that in the case of feeding itat the predetermined speed; wherein the reflective type determinationmeans having the image on the surface of the recording material readusing the image reading means while having the recording material fed bythe feeding control means so as to determine a predetermined attributeof the recording material by using obtained image on the surface of therecording material, wherein the image forming means determines a kind ofthe recording material based on an attribute obtained by the reflectivetype determination means so as to form the image on the recordingmaterial.
 2. The image forming apparatus according to claim 1, whereinthe reflective type determination means further includes calculationmeans for calculating data related to image reading noise by using theobtained image on the surface of the recording material and furtherhaving the image on the surface of the recording material read once bythe image reading means to eliminate the calculated data related to theimage reading noise from the one image obtained so as to determine thepredetermined attribute of the recording material by using the oneeliminated image.
 3. The image forming apparatus according to claim 1,wherein the feeding control means renders feeding speed on having therecording material read by the image reading means lower than thepredetermined speed so as to render the moving distance shorter thanthat in the case of feeding it at the predetermined speed.
 4. The imageforming apparatus according to claim 1, wherein the feeding controlmeans stops feeding the recording medium for a predetermined time eachtime the recording material is read by the image reading means so as torender the moving distance shorter than that in the case of feeding itat the predetermined speed.
 5. The image forming apparatus according toclaim 4, wherein the image reading means reads the image on the surfaceof the recording material in timing while the recording material is fedby the feeding control means.
 6. The image forming apparatus accordingto claim 1, wherein the reflective type determination means having theimage on the surface of the recording material read using the imagereading means a plurality of times while having the recording materialfed by the feeding control means so as to determine a predeterminedattribute of the recording material by using a plurality of obtainedimages on the surface of the recording material.
 7. An image formingapparatus comprising: feeding means for feeding a recording material atpredetermined speed in a predetermined direction; a latent imagesupporting element for supporting a latent image; and developing meansfor visualizing the latent image as a developed image by providing adeveloper to the latent image supporting element; transfer means fortransferring the developed image of the developing means to therecording material fed by the feeding means; fixing means for fixing therecording material having the developed image transferred thereon by thetransfer means; reflective type determination means including lightirradiation means for irradiating light on the recording material, imagereading means for reading the light irradiated by the light irradiationmeans and reflected from a surface of the recording material and therebyobtaining the image on the surface of the recording material, andfeeding control means for, on having the recording material read by theimage reading means, controlling the feeding means to render a movingdistance shorter than that in the case of feeding it at thepredetermined speed; wherein the reflective type determination meanshaving the image on the surface of the recording material read using theimage reading means while having the recording material fed by thefeeding control means so as to determine a predetermined attribute ofthe recording material by using obtained image on the surface of therecording material, wherein the developing means and fixing meansdetermine a kind of the recording material based on the attributeobtained by the reflective type determination means, and form thedeveloped image on the recording material according to an imageformation processing condition corresponding to the determined kind. 8.The image forming apparatus according to claim 7, wherein the reflectivetype determination means further includes calculation means forcalculating data related to the image reading noise by using theplurality of obtained mages on the surface of the recording material andfurther having the image on the surface of the recording material readby the image reading means once to eliminate the calculated data relatedto the image reading noise from the obtained one image so as todetermine a predetermined attribute of the recording material by usingthe one eliminated image.
 9. The image forming apparatus according toclaim 7, wherein the feeding control means renders the feeding speed onhaving the recording material read by the image reading means lower thanthe predetermined speed so as to render the moving distance shorter thanthat in the case of feeding it at the predetermined speed.
 10. The imageforming apparatus according to claim 7, wherein the feeding controlmeans stops the feeding for a predetermined time each time the recordingmaterial is read by the image reading means so as to render the movingdistance shorter then than that in the case of feeding it at thepredetermined speed.
 11. The image forming apparatus according to claim7, wherein the reflective type determination means having the image onthe surface of the recording material read using the image reading meansa plurality of times while having the recording material fed by thefeeding control means so as to determine a predetermined attribute ofthe recording material by using a plurality of obtained images on thesurface of the recording material.
 12. An image forming methodcomprising: a feeding step of feeding a recording material by feedingmeans at predetermined speed in a predetermined direction; a step ofhaving an image formed by image forming means on the recording materialfed by the feeding means; an image reading step of, while feeding therecording material by feeding means, reading by image reading meanslight irradiated by light irradiation means for irradiating the light onthe recording material and reflected from a surface of the recordingmaterial and thereby obtaining the image on the surface of the recordingmaterial; a reflective type determination step, including the imagereading step, of performing the image reading step so as to determine apredetermined attribute of the recording material by reflective typedetermination means by using obtained image on the surface of therecording material; and a step of determining a kind of the recordingmaterial based on the obtained attribute, wherein the reflective typedetermination step includes a step of, on having the recording materialread by the image reading means, having the feeding means controlled byfeeding control means to render a moving distance shorter then than thatin the case of feeding it at the predetermined speed.
 13. A recordingmaterial determination apparatus comprising: an image reading portionfor irradiating light on a recording medium and reading light reflectedfrom a surface of the recording medium and thereby obtaining an image onthe surface of the recording medium; a feeding portion for feeding therecording medium at a predetermined speed; a feeding control portionfor, on having the image on the recording medium read by the imagereading portion, controlling the feeding portion to feed the recordingmedium in a different feeding state from the feeding state in the caseof feeding it at the predetermined speed; and a determination portionfor having the image on the surface of the recording medium read by theimage reading portion while having the recording medium fed in thedifferent feeding state by the feeding portion so as to determine anattribute of the recording medium by using obtained images on thesurface of the recording medium.
 14. The recording materialdetermination apparatus according to claim 13, wherein the determinationportion calculates data related to image reading noise by using theobtained image on the surface of the recording medium and determines apredetermined attribute of the recording medium by using the datarelated to the image reading noise.
 15. The recording materialdetermination apparatus according to claim 13, wherein the differentfeeding state renders feeding speed of having the recording medium onhaving it read by the reading apparatus lower than the predeterminedspeed so as to render the moving distance of the recording mediumshorter then than that in the case of feeding it at the predeterminedspeed.
 16. The recording material determination apparatus according toclaim 13, wherein the feeding control portion stops the feeding of therecording medium for a predetermined time on having it read by thereading apparatus so as to render the moving distance of the recordingmedium shorter than that in the case of feeding it at the predeterminedspeed.
 17. The recording material determination apparatus according toclaim 16, wherein the reading apparatus reads the image on the surfaceof the recording medium in timing while the recording medium is fed. 18.The recording material determination apparatus according to claim 13,wherein the determination portion having the image on the surface of therecording material read using the image reading portion a plurality oftimes so as to determine a attribute of the recording material by usinga plurality of obtained images on the surface of the recording material.19. A recording material determination method comprising: a feeding stepof feeding a recording medium at a predetermined speed; an image readingstep of irradiating light on the recording medium and reading the lightirradiated and reflected from a surface of the recording medium andthereby obtaining an image on the surface of the recording medium; afeeding control step of, in the image reading step, controlling thefeeding operation of the recording medium to feed the recording mediumin a different feeding state from the feeding state in the case offeeding it at the predetermined speed; and a determination step ofhaving the image on the surface of the recording medium read, whilefeeding the recording medium in a different feeding state from thefeeding state in the case of feeding it at the predetermined speed inthe image reading step so as to determine an attribute of the recordingmedium by using obtained image on the surface of the recording medium.20. An image forming apparatus comprising: a feeding portion for feedingthe recording medium at a predetermined speed; an image forming portionfor forming an image on the recording material fed by the feedingportion; an reading portion for irradiating light on a recording mediumand reading light reflected from a surface of the recording medium andthereby obtaining an image on the surface of the recording medium; acontrol portion for having the image on the surface of the recordingmedium read by the reading portion while having the recording medium fedin a different feeding state by the feeding portion so as to change animage forming condition of the image forming portion by using obtainedimages on the surface of the recording medium.